Cushioning material for glass plate and glass laminate

Abstract

To obtain a cushioning material to be held between superposed glass plates, which suppresses adverse effects on the natural environment and has characteristics necessary for holding the superposed glass plates.SOLUTION: The cushioning material for glass plates is interposed between glass plates and is a powder containing ≥ 50 wt.% component of water-soluble inorganic salts. The preferred water-soluble inorganic salt particles are sodium chloride particles 303 having a cubic shape. The parallel flat surfaces of the sodium chloride particles 303 are in surface contact with the surfaces of the glass plates 301 and 302, and high adhesion is obtained.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a buffer material to be interposed between stacked glass sheets. [Background technology]

[0002] When transporting, storing, or handling glass plates, buffer material is inserted between each stack of glass plates to prevent scratches caused by contact between the glass plates. One technology uses powder made of synthetic resin particles (beads) with particle diameters of several tens to several hundreds of μm as the buffer material (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,611,546 Summary of the Invention [Problem to be solved by the invention]

[0004] There are concerns about the environmental impact of the powder used as the buffer material. For example, when the powder is applied to the surface of a glass plate, the powder falls off the surface. Although the powder that falls off the glass plate is collected, there is no guarantee that it is completely collected, and there is a risk that it may be released into the environment (for example, mixed with cleaning water and discharged into the sewer). Furthermore, the powder is removed from the surface of the glass plate during secondary processing (cutting or processing for productization), and the same risk exists at this time. Furthermore, although the amount is small, there is a possibility that the powder may scatter during transportation or transfer during the production process of glass plates laminated with the powder.

[0005] From the viewpoint of protecting the natural environment, it is undesirable to release synthetic resin powder into the environment. For example, there are concerns about the adverse effects of the accumulation of synthetic resin powder on fish, shellfish, birds, and animals.

[0006] On the other hand, glass plates are required to have high surface properties (flatness, absence of scratches and dirt), and in order to reliably protect the stacked glass plates during transportation, the powder held between the glass plates is also required to have high functionality (strength and retention).

[0007] In this context, the present invention aims to provide a highly functional material as a buffer material to be held between stacked glass sheets, which has a reduced adverse effect on the natural environment and has the functionality required to hold stacked glass sheets together. [Means for solving the problem]

[0008] The present invention relates to a buffer material for glass plates to be interposed between glass plates, the buffer material for glass plates including cubic-shaped particles having a coating layer. The present invention also relates to a buffer material for glass plates to be interposed between glass plates, the buffer material for glass plates being a powder containing 50% by weight or more of a component with a cubic crystal structure. In the present invention, the particles constituting the powder may have a sodium chloride-type crystal structure. In the present invention, the particles constituting the powder may have a cubic shape. In the present invention, the particles constituting the powder may have two parallel planes. In the present invention, the particles constituting the powder may have a flat surface.

[0009] In the present invention, the particles constituting the powder may be at least one of sodium chloride particles, magnesium oxide particles, and alum particles. In the present invention, the particles may have an equivalent circle diameter of 10 μm to 250 μm. In the present invention, the surfaces of the particles may be coated with a biodegradable resin. [Effects of the Invention]

[0010] According to the present invention, a buffer material to be held between stacked glass sheets can be obtained that has a reduced adverse effect on the natural environment and has the function required to hold the stacked glass sheets together. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram of an embodiment. [Figure 2] 1 is a drawing-substitute photograph showing a microscope photograph of sodium chloride particles. [Figure 3] FIG. 1 is an image diagram showing the cross-sectional structure of a sodium chloride particle having a coating layer. [Figure 4] 1 is a drawing-substitute photograph showing a microscope photograph of sodium chloride particles without a coating layer. [Figure 5] 1 is a drawing-substitute photograph showing a microscope photograph of sodium chloride particles with a coating layer. [Figure 6] FIG. 1 is an image diagram showing a method for measuring adhesion to a glass plate. [Figure 7] 1 is a graph showing the results of measuring the adhesion of sodium chloride particles and acrylic resin particles to a glass plate. [Figure 8] FIG. 1 is an image diagram showing the state of adhesion of cubic sodium chloride particles to a glass plate. [Figure 9] 1 is a graph showing the relationship between pressure applied to sodium chloride particles and the amount of deformation. [Figure 10] 1 is a graph showing the relationship between the pressure applied to acrylic particles and the amount of deformation. [Figure 11] 1 is a graph showing the relationship between the pressure applied to a particle of Glauber's salt and the amount of deformation. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. First embodiment (overview) The powder of the buffer material for glass plates shown in this embodiment has the following characteristics. (1) It has little adverse impact on the environment. (2) High adhesion to glass plates due to particle shape. (3) High dispersibility when applied to the surface of a glass plate. (4) Sufficient strength to hold the stacked glass panes together. (5) The glass is less likely to get dirty. (6) Easy to clean.

[0013] Fig. 1 shows four glass plates 101, 102, 103, and 104 stacked one on top of the other. The number of glass plates to be stacked is not limited, and two or more plates are possible. Here, four plates are shown as an example. The applications of the glass plates are not limited, and examples include architecture, vehicles, displays, and solar cells.

[0014] A particle layer 111 is provided between the glass plates 101 and 102, a particle layer 112 is provided between the glass plates 102 and 103, and a particle layer 113 is provided between the glass plates 103 and 104.

[0015] The particulate layer 111 functions as a buffer layer to prevent direct contact between the glass plates 101 and 102. The particulate layers 112 to 113 also have the same function. The particulate layers 111 to 113 also have the function of holding the adjacent glass plates vertically so that they do not move relative to each other due to vibration or impact, and the function of absorbing vibration and impact. The thickness of the particulate layers 111 to 113 is approximately 10 μm to 400 μm, and preferably approximately 50 μm to 150 μm.

[0016] (Particles that make up the particle layer) The particle layers 111 to 113 are mainly composed of sodium chloride (NaCl) powder. Each of the particle layers 111 to 113 contains 50% to 99.9% by weight of sodium chloride (NaCl) component, preferably 80% to 99.9% by weight, and more preferably 95% to 99.9% by weight, with the remainder being a coating layer covering the sodium chloride particles, additives added as needed, or unavoidable impurities.

[0017] The particles (sodium chloride particles) that make up sodium chloride powder have a cubic (regular hexahedral) shape. Cubic sodium chloride particles are obtained by isotropic crystal growth. Cubic shapes also include shapes with rounded corners. In this case, a shape in which 80% or more of the surface is flat is preferred. The term "particle" refers to individual grains.

[0018] The particle size of the sodium chloride particles is understood as the equivalent circle diameter, and is 10 μm to 400 μm on average, preferably 10 μm to 250 μm. Fig. 2 is a microscope photograph of the sodium chloride particles used in this embodiment.

[0019] As shown in Figure 2, the sodium chloride particles used in this embodiment have a cubic (dice) shape. The particle size distribution of the sodium chloride powder is preferably narrow (sharp). By narrowing the distribution, the amount of unnecessary (small) particles that do not support the glass can be reduced, making it more economical.

[0020] Sodium chloride has a sodium chloride type crystal structure, which is one of the cubic crystal structures. This crystal structure is the basic structure of a cubic (regular hexahedron) particle shape. The cubic sodium chloride particles used in this embodiment are obtained by isotropically growing the basic cubic crystal structure.

[0021] Cubic sodium chloride particles have parallel flat faces. These faces come into surface contact with the glass surface, which allows the powder composed of the sodium chloride particles to adhere well to the glass plate, as described below. This effect is true for all particles obtained by isotropically growing a cubic crystal structure.

[0022] (coating layer) The sodium chloride particles used in this embodiment are covered on their surfaces with a biodegradable coating layer (covering layer). Known biodegradable materials can be used for the coating. An example of the biodegradable material is water-soluble cellulose. Here, an aqueous solution of water-soluble cellulose is spray-coated onto the surfaces of the sodium chloride particles to form a water-soluble cellulose coating layer on the surfaces of the sodium chloride particles. The thickness of the coating layer when dried is 1 μm to 20 μm, preferably about 2 μm to 10 μm. The proportion of the water-soluble cellulose component in the coating layer is 50 wt % or more.

[0023] Spray coating is a method in which particles are suspended in an air current to form a fluidized bed, and an aqueous solution containing a coating material is sprayed onto the fluidized bed to adhere the coating material to the particle surface and then dried, forming a coating layer. In spray coating, the thickness of the coating layer can be controlled by adjusting the temperature and air volume of the air current used to form the fluidized bed, as well as the concentration and spraying conditions of the aqueous solution containing the coating material.

[0024] 3 is a cross-sectional image diagram of sodium chloride particles 150 coated with coating layer 151. By providing coating layer 151, the dispersibility of powder constituted by sodium chloride particles 150 can be improved.

[0025] Figure 4 is a microscope photograph of uncoated sodium chloride particles scattered on a glass plate. Table 1 shows the particle size distribution of the uncoated sodium chloride particles shown in Figure 4.

[0026] [Table 1]

[0027] Figure 5 is a microscope photograph of coated sodium chloride particles scattered on a glass plate. Table 2 shows the particle size distribution of the coated sodium chloride particles shown in Figure 5.

[0028] [Table 2]

[0029] The coating layer in Figure 5 is a layer of water-soluble cellulose, and its thickness is approximately 4 μm. Here, "Metolose" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd. was used as the water-soluble cellulose. Spray coating was performed using a fluidized bed device MP01 manufactured by Powrex Corporation.

[0030] As is clear from a comparison of FIG. 4 and FIG. 5, the provision of a coating layer improves the dispersibility of sodium chloride particles.

[0031] Table 3 shows data on the dispersibility of sodium chloride particles (shown in Figure 4) on a glass plate that does not have a water-soluble cellulose coating layer. Sodium chloride powder was spread on a glass slide, images were taken with a microscope, and the dispersion rate was calculated after counting the number of particles. In Table 3, dispersed particles are separated (isolated) particles, and agglomerated particles are particles in which two or more particles have aggregated and can be considered as a single particle.

[0032] Dispersion is the ratio of particles that can be considered as a single isolated particle to all particles being measured on the glass plate. A dispersion of 100% occurs when all particles being measured are observed as a single isolated particle. The higher the dispersion, the more uniformly the particles are distributed on the glass plate. The lower the dispersion, the greater the proportion of particles in a state where two or more particles are aggregated, and the greater the tendency for the particle distribution to become non-uniform.

[0033] [Table 3]

[0034] Table 4 shows data on the dispersibility of sodium chloride particles with a water-soluble cellulose coating layer, as shown in Figure 5, on a glass plate. The experimental conditions are the same as those in Table 3.

[0035] [Table 4]

[0036] Tables 3 and 4 show the high dispersibility of sodium chloride particles with a coating layer. Table 5 shows data on the dispersibility of acrylic powder. Table 6 shows the particle size distribution of the acrylic particles in Table 5. As shown in Table 5, the dispersibility of acrylic particles is poorer than that of sodium chloride particles with a coating layer. In addition, acrylic particles have a high electrostatic charge, and in actual use, their dispersibility tends to be lower than the data in Table 5.

[0037] [Table 5]

[0038] [Table 6]

[0039] High dispersibility means that the powder has high fluidity. In the process of spraying the powder onto the glass plates, it is desirable that the powder be sprayed with good dispersibility without agglomeration. If the particle dispersibility is poor, the retaining layer that holds the stacked glass plates tends to be uneven (tend to be patchy). If the retaining layer becomes uneven, partial gaps will be created, which increases the possibility of glass tarnish, which is undesirable. In this regard, providing the above-mentioned coating layer is highly effective in increasing the dispersibility of the particles.

[0040] The coating layer also functions to prevent sodium chloride components from coming into direct contact with the glass plate surface. Direct contact of sodium and chlorine components with the glass plate surface can cause scale marks, which are scale-like patterns. By providing coating layer 151, this problem can be prevented.

[0041] Incidentally, there is a known problem of glass tarnish caused by the elution of alkaline components from the interior of the glass sheet onto the surface of the glass sheet. One method for suppressing this phenomenon is to supply alkaline components to the surface of the glass sheet from the outside, thereby suppressing the elution of alkaline components from the interior of the glass sheet. The coating layer 151 also functions as a buffer layer that ensures the appropriate supply of alkaline components from the sodium chloride particles 150 to the surface of the glass sheet. Therefore, the coating layer 151 has the function of preventing the occurrence of the above-mentioned scale marks caused by the material of the sodium chloride particles 150 themselves, and the function of suppressing the occurrence of glass tarnish by the appropriate supply of alkaline components to the surface of the glass sheet.

[0042] In addition to cellulose, organic acids (adipic acid, succinic acid, citric acid), water-soluble inorganic salts (such as Glauber's salt), sodium acetate (sodium salt of an organic acid), PLA (biodegradable resin), and the like, as well as combinations of two or more of these materials, can be used as materials for forming the coating layer 151. A spray coating method can be used as a method for forming a coating layer made of these materials.

[0043] The spray coating method can be used regardless of whether the material to be coated is water-soluble or not. For water-soluble materials, an aqueous solution of the material is used as the spray solution. For water-insoluble or poorly water-soluble materials, a liquid in which fine powder of the material is dispersed is used as the spray solution. For water-insoluble or poorly water-soluble materials, the particle size of the fine powder particles should be 10% or less, preferably 5% or less, of the particle size of the base particle. In this case, a coating layer is formed in which many particles of the fine powder cling to the surface of the base particle.

[0044] For example, suppose a coating layer of adipic acid is formed on cellulose particles with an average particle size of 150 μm. In this case, a coating layer of the desired thickness is formed by a spray coating method using a liquid containing adipic acid particles with an average particle size of 1 μm as the spray liquid. In this case, the surface of the cellulose particles is covered with a large number of adipic acid particles distributed in layers. The coating layer is formed by the large number of adipic acid particles distributed in layers.

[0045] The coating layer may also contain a biodegradable material and a water-soluble inorganic salt and / or an organic acid. For example, the coating layer may be formed by a spray coating method using an aqueous solution containing water-soluble cellulose and water-soluble inorganic salts as the spray liquid, or by a spray coating method using an aqueous solution containing water-soluble cellulose and organic acid particles as the spray liquid.

[0046] (Adhesion to glass plate) Figure 6 is an image diagram showing a method for measuring adhesion to a glass plate. In the method shown in Figure 6, powder is first scattered on a horizontal glass plate, and then the glass plate is held upright and impacted with a hammer. The total area of ​​the powder adhering to the surface of the glass plate before and after the impact is determined by image analysis, and the particle retention rate is calculated by dividing the total area of ​​the particles adhering after the impact by the total area of ​​the particles adhering before the impact. The particle retention rate is the proportion of powder that did not fall off from the surface of the glass plate due to the impact.

[0047] Table 7 shows the measurement results of the particle residue rate of sodium chloride particles and acrylic particles (PMMA) on a glass plate. The horizontal axis is the hammer angle in Figure 6. Table 7 shows the measurement results on which Figure 7 is based. The hammer angle corresponds to the impact acceleration applied to the glass plate. The larger the hammer angle, the greater the impact acceleration applied to the glass plate. According to the findings of the inventors, as a rough guide, the impact acceleration applied to the glass plate at a hammer angle of 30° was 100 G, the impact acceleration applied to the glass plate at a hammer angle of 45° was 390 G, and the impact acceleration applied to the glass plate at a hammer angle of 60° was 680 G.

[0048] [Table 7]

[0049] The sodium chloride particles used had the particle shape shown in Figure 2 and the particle size distribution shown in Table 1. The PMMA sample used had the particle size distribution shown in Table 6. The sample shown in Figure 7 did not have a biodegradable coating layer.

[0050] PMMA powder is currently used in the industry as a buffer material for glass plates. Therefore, it can be said that sodium chloride particles with the particle shapes shown in Figure 7 and Figure 2 have high adhesiveness equal to or higher than the appropriate adhesiveness of PMMA.

[0051] (Considerations regarding adhesion) Figure 8 is an image diagram showing the state of particles adhering to glass plates. Figure 8(A) shows a state in which a spherical particle 203 (e.g., an acrylic particle) is held between glass plates 201 and 202. Figure 8(B) shows a state in which a cubic particle 303 (e.g., a sodium chloride particle) is held between glass plates 301 and 302.

[0052] In the case of Figure 8(A), the particles come into close to point contact with the glass plate. In contrast, in the case of Figure 8(B), the particles come into area contact with the glass plate. For the same material, the adhesion force of the particles to the glass plate surface increases as the contact area increases. When considering the contribution to adhesion, the difference between point contact and area contact is large, and this is thought to be the reason for the good adhesion (high adhesion) of sodium chloride powder to the glass plate.

[0053] In particular, cubic particles have three sets of parallel flat surfaces that intersect at right angles and ideally have the same area, so there is a high probability that two flat surfaces of each particle will come into contact with the opposing glass surface, resulting in particularly high adhesion to the glass surface and therefore high adhesion to the glass surface.

[0054] (particle strength) Deformation strength was measured as particle strength. Elastic-plastic or malleable materials often undergo continuous deformation without breaking. Therefore, we focused on the degree of deformation and measured the applied force when the particle was compressed to 50% of its diameter as deformation strength.

[0055] Measurements were carried out on 10 samples using a microparticle crushing force measuring device (NS-A300 model, manufactured by Nano Seeds Co., Ltd.). During the measurement, the particles were pressed into the crushing needle, and a waveform chart of the pressing force was recorded. The amount of deformation was also measured from the displacement of the crushing needle.

[0056] The deformation strength is σ 10% =F 10% / A (JIS Z 8844), where σ 10% is the deformation strength (Pa) for a compressive displacement of 10% of the particle diameter. F 10% is the test force (N) for a compressive displacement of 10% of the particle diameter. A is the area (m 2 ) The particle size was measured by image analysis. Here, the deformation strength σ, which is stronger than the JIS standard, is 50% The measurement data relating to particle strength are shown in Table 8. The measurement was carried out on particles without a coating layer.

[0057] [Table 8]

[0058] Acrylic particles are used in practical applications as a buffer material for glass plates. Figures 9 to 11 are graphs showing the relationship between the force (vertical axis) applied by a crushing needle to each particle measured using the above-mentioned microparticle crushing force measuring device and the amount of particle deformation. Figure 9 shows data for sodium chloride particles, Figure 10 for acrylic particles, and Figure 11 for Glauber's salt particles. It can be seen that the sodium chloride particles in Figure 9 and the acrylic particles in Figure 10 deform in roughly proportion to the pressing force. The waveform distortion in the data for Glauber's salt particles in Figure 11 indicates that the particles have been crushed by pressure. From these findings, it can be said that sodium chloride particles have sufficient strength required for a buffer material for glass plates.

[0059] Furthermore, the sodium chloride particles in Figure 9 exhibit deformation closer to elastic deformation than the acrylic particles in Figure 10. This means that when used as a buffer material for glass plates, the sodium chloride particles can more effectively absorb shocks and vibrations applied to a stack of glass plates than the acrylic particles.

[0060] Example 1 For the particle layers 111 to 113 in FIG. 1, sodium chloride powder having the particle shape shown in FIG. 2 and the particle size distribution shown in Table 2 was used.

[0061] The particles (sodium chloride particles) constituting this sodium chloride powder were coated with a water-soluble cellulose solution by spray coating the surface of the sodium chloride particles with a water-soluble cellulose coating layer. The thickness of the coating layer (when dry) was 4 μm. As the water-soluble cellulose, "Metolose" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd. was used. The spray coating was carried out using a fluidized bed apparatus MP01 manufactured by Powrex Corporation.

[0062] Example 2 Table 9 shows another example of the measured values ​​for acrylic particles and sodium chloride particles without a coating layer. The sodium chloride particles have a cubic shape as shown in Figure 2. The average adhesive strength is the adhesive strength to a glass plate.

[0063] Adhesion was measured using a centrifugal adhesion measuring device (NS-C100 model manufactured by Nano Seeds Co., Ltd.) In this measurement, a sample was attached to the surface of a substrate (glass plate), and the substrate was then centrifuged at six levels of pressure from 100G to 800G in a centrifuge, and the state of particle separation was recorded as an image, and the particle retention rate after rotation was measured relative to the initial number of particles attached before centrifugation.

[0064] The adhesion force of the particle to the substrate is equal to the centrifugal separation force acting on the particle, F=(π / 6)ρd 3 rω 2 where ρ is the true density of the particles, d is the particle diameter, r is the rotation radius of the centrifuge, and ω is the rotation angular velocity of the centrifuge. The particle retention rate after rotation was plotted on the horizontal axis, and the particle separation force at each rotation point was plotted on the vertical axis, and the average adhesion force (separation force at which 50% of the particles separate) was calculated from the exponential approximation curve.

[0065] [Table 9]

[0066] From Table 9, it can be seen that the sodium chloride particles have high strength and good adhesion to the glass plate.

[0067] Example 3 The test shown in Figure 6 was carried out on sodium chloride particles with a water-soluble cellulose coating layer (Table 2) and sodium chloride particles without a coating layer (Table 1). Tables 10 and 11 show the test results (particle residual rate).

[0068] [Table 10]

[0069] [Table 11]

[0070] The adhesion of coated sodium chloride particles to glass plates is lower than that of uncoated particles. However, the impact tests at hammer angles of 45° and 60° are fairly severe test conditions, and it is believed that coated sodium chloride particles also have adhesion to practical impacts.

[0071] Example 4 It is also possible to incorporate organic acid particles into a coating layer of sodium chloride particles. In this case, the particle size of the organic acid is approximately equal to or smaller than the thickness of the coating layer. For example, the coating layer is composed of fine powders of water-soluble cellulose and adipic acid. The sodium chloride particles in Table 1 are used as base particles. The coating layer is formed by a spray coating method using a spray liquid in which an aqueous solution of water-soluble cellulose is mixed with adipic acid having an average particle size of 2 μm. The thickness of the coating layer is approximately 5 μm. The mixing ratio of water-soluble cellulose to adipic acid is 90:10 to 99:1, for example 95:5, by weight when dry.

[0072] In this example, adipic acid particles are incorporated into a coating layer of water-soluble cellulose. This coating layer structure is expected to provide high dispersibility and prevent glass tarnish due to the incorporated adipic acid particles, as well as improve adhesion to glass plates.

[0073] Example 5 The coating layer is made of a fine powder of organic acid. In this example, the coating layer is made of a fine powder of adipic acid. The base particles are sodium chloride particles shown in Table 1. The coating layer is formed using a spray coating method, with the spray liquid containing adipic acid with an average particle size of 1 μm. The thickness of the coating layer is approximately 5 μm. In this example, the coating layer is formed by a large number of adipic acid particles distributed in a shell shape.

[0074] (superiority) Sodium chloride powder has the following advantages as a buffer material for glass plates: (1) It has little adverse impact on the environment. (2) High adhesion to glass plates due to particle shape. (3) High dispersibility when applied to the surface of a glass plate. (4) Sufficient strength to hold the stacked glass panes together. (5) The glass is less likely to get dirty. (6) Easy to clean.

[0075] Sodium chloride is a natural substance found in nature and has less of a negative impact on the environment than synthetic resin particles.

[0076] A powder buffer material for glass plates is required to have high adhesion to the glass plates. In this regard, as shown in Figure 8, cubic sodium chloride particles 303 have parallel flat faces that come into surface contact with the surfaces of glass plates 301 and 302, thereby achieving high adhesion.

[0077] Current acrylic powders have the problem of poor dispersibility on glass plates (see Table 5). If the powder disperses poorly on glass plates, the powder will not be distributed uniformly between stacked glass plates, leaving gaps where there is no particle layer. If stacked glass plates are stored for a long period of time, these gaps may cause glass discoloration. The sodium chloride powder with a coating layer has high dispersibility, which reduces the problems caused by the presence of the above-mentioned non-uniform particle layer.

[0078] Furthermore, the particles of the powder-based buffer material for glass plates must be strong because, if the particles are broken by the pressure applied when the glass plates are stacked, this will cause contact between the glass plates and damage to the glass plate surfaces. The cubic sodium chloride particles are crystalline and have the strength required for a buffer material for glass plates.

[0079] By providing a water-soluble cellulose coating layer on the surface of sodium chloride particles, the sodium chloride component can be prevented from coming into direct contact with the glass, thereby suppressing contamination of the glass by the sodium chloride component. In addition, the sodium chloride can be easily removed from the glass surface by rinsing with water, making cleaning easy.

[0080] 2. Other Embodiments Examples of particles having a sodium chloride-type crystal structure include magnesium oxide particles. Examples of particles having a cubic crystal structure include alum particles (potassium alum, etc.). These particles are also obtained by isotropically growing a basic crystal structure. These particles also have flat surfaces and provide good adhesion to glass plates, similar to the sodium chloride particles described above. The particle size, coating layer formation, etc. are the same as those described in the specification. Magnesium oxide and alum are naturally occurring substances and do not have the adverse environmental impact that synthetic resins do. It is also possible to use a mixture of two or more of sodium chloride particles, magnesium oxide particles, and alum particles.

[0081] 3.Other Powders composed of particles having a cubic crystal structure as exemplified herein can also be dried and charged, which can improve adhesion to glass plates.

[0082] As shown in Tables 10 and 11, sodium chloride particles with a water-soluble cellulose coating layer exhibit reduced adhesion to glass plates compared to particles without the coating layer. One way to prevent this reduction is to hydrophobize the water-soluble cellulose coating layer. Hydrophobization makes it difficult for the particles to adsorb moisture, increasing their chargeability. This improves adhesion to glass plates. Examples of hydrophobization treatments include fluorine plasma treatment and plasma treatment in a reducing atmosphere using hydrocarbons (e.g., methanol).

[0083] Various additives can also be used, and these additives can be introduced by (1) mixing them as particles, (2) mixing an aqueous solution containing the additive with a coating liquid for forming a coating layer made of a biodegradable resin, or (3) forming an additional coating layer on the surface of base particles using an aqueous solution or sol containing the additive, separate from the coating layer made of a biodegradable resin.

[0084] According to the technology disclosed in this specification, it is possible to obtain a glass laminate that has a reduced impact on the natural environment and meets the requirements for holding glass sheets stacked together. [Explanation of symbols]

[0085] 101...glass plate, 102...glass plate, 103...glass plate, 104...glass plate, 111...particle layer, 112...particle layer, 113...particle layer, 150...sodium chloride particles, 151...coating layer, 201...glass plate, 202...glass plate, 203...spherical particles, 301...glass plate, 302...glass plate, 303...cubic-shaped particles (sodium chloride particles).

Claims

1. A buffer material for glass plates to be placed between glass plates, the buffer material comprising cubic particles having a coating layer.

2. the coating layer contains water-soluble cellulose, 2. The buffer material for glass plates according to claim 1, wherein the particles are sodium chloride particles.

3. A buffer material for glass plates, which is a powder containing 50% by weight or more of components with a cubic crystal structure, to be placed between glass plates.

4. 4. The buffer material for glass plates according to claim 3, wherein the particles constituting the powder have a sodium chloride type crystal structure.

5. 4. The buffer material for glass plates according to claim 3, wherein the particles constituting the powder have a cubic shape.

6. 4. The buffer material for glass plates according to claim 3, wherein the particles constituting the powder have two parallel flat surfaces.

7. 4. The buffer material for glass plates according to claim 3, wherein the particles constituting the powder have flat surfaces.

8. 8. The buffer material for glass plates according to claim 3, wherein the particles constituting the powder are at least one of sodium chloride particles, magnesium oxide particles, and alum particles.

9. 8. The buffer material for glass plates according to claim 3, wherein the particles constituting the powder have an equivalent circle diameter of 10 μm to 250 μm.

10. 8. The buffer material for glass plates according to claim 3, wherein the surfaces of the particles constituting the powder are covered with a biodegradable coating layer.

11. The buffer material for glass plates according to claim 10 , wherein the coating layer contains a water-soluble inorganic salt and / or an organic acid.

12. the particles constituting the powder are sodium chloride particles, the surfaces of the particles constituting the powder are covered with a coating layer of water-soluble cellulose, When dispersed on a glass plate, The isolated particles are called dispersed particles, The dispersion ratio is defined as (number of dispersed particles / total number of particles), 4. The buffer material for glass plates according to claim 3, wherein the dispersion rate of the powder is 80% or more.

13. A buffer material for glass plates to be placed between glass plates, the buffer material being a powder containing 50% by weight or more of cubic particles.

14. A buffer material for glass plates to be interposed between glass plates, A buffer material for glass plates, which is a powder having a cubic crystal structure and containing 50% by weight or more of particles that have been formed into a cubic shape by isotropically growing the cubic crystal structure.

15. A glass laminate in which at least two glass plates are laminated via a buffer material for glass plates, The glass laminate, wherein the buffer material for the glass plate is a powder containing 50% by weight or more of a component with a cubic crystal structure.

16. A glass laminate in which at least two glass plates are laminated via a buffer material for glass plates, The buffer material for glass plates is a powder containing particles having two parallel flat surfaces, A glass laminate in which one of the two parallel planes is in contact with a surface of one of the two glass plates, and the other of the two parallel planes is in contact with a surface of the other of the two glass plates.

17. 17. The glass laminate according to claim 15 or 16, wherein the particles constituting the powder are at least one of sodium chloride particles, magnesium oxide particles, and alum particles.

Images