Cushioning material for glass plates and glass laminate

Abstract

[Problem] To provide a cushioning material held between glass plates laid on top of one another, with which undesirable impact on natural environment is limited, and which has the necessary characteristics to hold the glass plates in an overlaid condition. [Solution] This cushioning material for glass plates, which is interposed between the glass plates, is a powder containing 50 wt.% or more of a water-soluble inorganic salt component. Preferable water-soluble inorganic salt particles are sodium chloride particles 303 having a cubic shape. The sodium chloride particles 303 are such that parallel flat surfaces thereof are brought into surface contact with the surfaces of glass plates 301 and 302, whereby high adhesion is achieved.

Description

Buffer material for glass plates and glass laminate

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

[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 technique 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).

[0003] U.S. Patent No. 10,611,546

[0004] There are concerns about the environmental impact of the powder used as the buffer material. For example, when the powder is sprayed onto the surface of a glass plate, the powder falls off the surface of the glass plate. 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 flowing into the sewer). Furthermore, the powder is removed from the surface of the glass plate during secondary processing (cutting or processing for productization), and there is a similar risk in this case. Furthermore, although the amount is small, there is a possibility that the powder may scatter during transportation or transfer in the production process of glass plates laminated via 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 stains), 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.

[0008] The present invention provides a buffer material for glass plates to be placed between glass plates, the buffer material comprising cubic-shaped particles having a coating layer, the coating layer comprising water-soluble cellulose, the particles being sodium chloride particles, and the buffer material for glass plates containing 50% by weight or more of the sodium chloride particle component. The present invention also provides a buffer material for glass plates to be placed between glass plates, the buffer material comprising a powder containing 50% by weight or more of a component with a cubic crystal structure, the particles comprising the powder being cubic-shaped sodium chloride particles. In an embodiment of the present invention, the particles have an equivalent circle diameter of 10 μm to 250 μm. In an embodiment of the present invention, the particles have a cellulose coating layer.

[0009] The present invention provides a glass laminate comprising at least two glass plates laminated together via a buffer material for the glass plates, the buffer material being a powder containing 50% by weight or more of sodium chloride particles having a cubic crystal structure. The present invention provides a glass laminate comprising at least two glass plates laminated together via a buffer material for the glass plates, the buffer material being a powder containing 50% by weight or more of sodium chloride particles having two parallel planes, one of the two parallel planes being in contact with a surface of one of the two glass plates and the other of the two parallel planes being in contact with a surface of the other of the two glass plates.

[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.

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

[0012] 1. First Embodiment (Summary) The powder of the buffer material for glass plates shown in this embodiment has the following characteristics: (1) Little adverse effect on the environment. (2) High adhesion to glass plates due to the particle shape. (3) High dispersibility when applied to the surface of the glass plate. (4) Sufficient strength to hold stacked glass plates together. (5) 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 particle layer 111 functions as a buffer layer that prevents direct contact between the glass plate 101 and the glass plate 102. This function is also shared by the particle layers 112 to 113. The particle 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 particle layers 111 to 113 is approximately 10 μm to 400 μm, preferably approximately 50 μm to 150 μm.

[0016] (Particles Constituting the Particle Layer) The particle layers 111 to 113 are primarily composed of sodium chloride (NaCl) powder. Each of the particle layers 111 to 113 contains 50 wt % to 99.9 wt %, preferably 80 wt % to 99.9 wt %, and more preferably 95 wt % to 99.9 wt % of the sodium chloride (NaCl) component, with the remainder consisting of a coating layer covering the sodium chloride particles, additives added as needed, or unavoidable impurities.

[0017] The particles (sodium chloride particles) that make up the sodium chloride powder have a cubic (regular hexahedral) shape. Cubic sodium chloride particles are obtained by isotropic crystal growth. The cubic shape also includes 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 determined by the equivalent circle diameter, and is 10 μm to 400 μm on average, preferably 10 μm to 250 μm. Figure 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-like) 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 the powder constituted by sodium chloride particles 150 can be improved.

[0025] Figure 4 is a microscope photograph of sodium chloride particles without a coating layer scattered on a glass plate. Table 1 shows the particle size distribution of the sodium chloride particles without a coating layer in Figure 4.

[0026]

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

[0028]

[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 dispersibility of sodium chloride particles is improved by providing a coating layer.

[0031] Table 3 shows data showing the dispersibility of the sodium chloride particles shown in Figure 4, which do not have a water-soluble cellulose coating layer, on a glass plate. Sodium chloride powder was spread on a glass slide, images were taken with a microscope, and the number of particles was counted before calculating the dispersion ratio. 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] The dispersion ratio is the proportion of particles that can be considered as a single isolated particle to all particles to be measured on the glass plate. A dispersion ratio of 100% occurs when all particles to be measured are observed as a single isolated particle. The higher the dispersion ratio, the more uniformly the particles are distributed on the glass plate. The smaller the dispersion ratio, 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]

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

[0035]

[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]

[0038]

[0039] High dispersibility means high fluidity of the powder. In the process of spraying the powder onto the glass plate, it is desirable that the powder can 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 generated, 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 direct contact of sodium chloride components with the glass sheet surface. Direct contact of sodium and chlorine components with the glass sheet 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 scale-like 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, materials that can be used to form the coating layer 151 include 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. A spray coating method can be used to form 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 is 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 a 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 a spray liquid. In this case, the surface of the cellulose particles is covered with a large number of adipic acid fine particles distributed in layers. The coating layer is formed by the large number of adipic acid fine 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 a water-soluble inorganic salt 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) Fig. 6 is an image diagram showing a method for measuring adhesion to a glass plate. In the method shown in Fig. 6, powder is first scattered on a horizontally placed glass plate, and then the glass plate is placed vertically and impacted with a hammer. The total area of ​​the powder adhering to the surface of the glass plate before and after the impact in photographed images is determined by image analysis, and the particle residual rate is calculated by (total area of ​​particles adhering after impact) / (total area of ​​particles adhering before impact). The particle residual rate is the proportion of powder that did not fall off from the surface of the glass plate due to the impact.

[0047] FIG. 7 shows the measurement results of particle residue rates of sodium chloride particles and acrylic particles (PMMA) on a glass plate. The horizontal axis represents the hammer angle in FIG. 6. Table 7 shows the measurement results on which FIG. 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]

[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, based on the results of Figure 7, it can be said that sodium chloride particles with the particle shape shown in Figure 2 have adhesive properties equal to or greater than the appropriate adhesive properties of PMMA.

[0051] (Considerations on 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 contact of the particles with the glass plate is close to point contact. In contrast, in the case of Figure 8(B), the contact of the particles with the glass plate is area contact. For the same material, the adhesive force of the particles to the glass plate surface increases as the contact area increases. When considering the contribution to adhesive force, the difference between the point contact and area contact is large, and this is thought to be the reason for the good adhesion (high adhesive force) 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 plate surface and therefore high adhesion to the glass plate surface.

[0054] (Particle strength) The deformation strength was measured as particle strength. Elastic-plastic or malleable materials often undergo continuous deformation without breaking. Therefore, focusing on the degree of deformation, the applied force when compressively displaced by 50% of the particle diameter was measured as the deformation strength.

[0055] Measurements were performed on 10 samples using a microparticle crushing force measuring device (NS-A300 model, manufactured by Nano Seeds Corporation). 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. 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 the strength of the particles are shown in Table 8. The measurement was carried out on particles without a coating layer.

[0057]

[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) exerted by a crushing needle on each particle measured using the 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 force applied. 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 Fig. 9 exhibit deformation closer to elastic deformation than the acrylic particles in Fig. 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. The thickness of the coating layer (when dry) was 4 μm. The water-soluble cellulose used was "Metolose" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd. The spray coating was performed using a fluidized bed device MP01 manufactured by Powrex Corporation.

[0062] (Example 2) Table 9 shows the measured values ​​of deformation strength and the like of 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] The adhesive force was measured using a centrifugal adhesive force 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 centrifuged at six levels of 100 G to 800 G in a centrifuge, the state of particle separation was recorded as an image, and the particle residual rate after rotation was measured relative to the initial number of attached particles before centrifugation.

[0064] The adhesion force of the particles to the substrate is equal to the centrifugal separation force acting on the particles, 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 part 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]

[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 provided with a water-soluble cellulose coating layer shown in Table 2 and sodium chloride particles not provided with a coating layer shown in Table 1. Tables 10 and 11 show the test results (particle residual rate).

[0068]

[0069]

[0070] The adhesion of the sodium chloride particles with a coating layer to the glass plate is lower than that of the particles without a coating layer. However, the impact tests at hammer angles of 45° and 60° are fairly severe test conditions, and it is believed that the sodium chloride particles with a coating layer 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 set to approximately the thickness of the coating layer or less. 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 the 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 an 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, and a spray liquid containing adipic acid with an average particle size of 1 μm is used. The thickness of the coating layer is approximately 5 μm. In this example, the coating layer is formed from a large number of adipic acid particles distributed in a shell shape.

[0074] (Advantages) Sodium chloride powder has the following advantages as a buffer material for glass plates: (1) Little adverse impact on the environment. (2) High adhesion to glass plates due to the particle shape. (3) High dispersibility when applied to the surface of glass plates. (4) Sufficient strength to hold stacked glass plates together. (5) 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 surfaces 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). Poor dispersibility of the powder on glass plates results in uneven distribution of the powder between stacked glass plates, resulting in the formation of gaps where the particle layer is absent. When stacked glass plates are stored for an extended period of time, glass discoloration may occur in these gaps. The sodium chloride powder with a coating layer formed on it has high dispersibility, which prevents the problems caused by the presence of the 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 is prevented from coming into direct contact with the glass, preventing 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 Particles having a sodium chloride-type crystal structure include magnesium oxide particles. Furthermore, 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 exhibit good adhesion to glass plates, similar to the sodium chloride particles described above. The particle size, coating layer formation, and other details 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 of synthetic resins. It is also possible to use a mixture of two or more of sodium chloride particles, magnesium oxide particles, and alum particles.

[0081] 3. It is also possible to dry or charge a powder composed of particles having a cubic crystal structure as exemplified in this specification. By drying or charging the powder, the adhesion to the glass plate can be improved.

[0082] As shown in Tables 10 and 11, sodium chloride particles provided with a water-soluble cellulose coating layer exhibit reduced adhesion to glass plates compared to particles without the coating layer. One possible method for suppressing 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 treatments for hydrophobizing 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 the following methods: (1) mixing them as particles, (2) mixing the aforementioned aqueous solution containing the additive with a coating liquid for forming a coating layer of biodegradable resin, and forming them on the surface of the base particles, or (3) forming a further coating layer on the surface of the base particles using an aqueous solution or sol containing the additive, separate from the coating layer of biodegradable resin.

[0084] The technology disclosed in this specification provides a glass laminate that minimizes environmental impact and meets the requirements for stacking and holding glass sheets together. The invention disclosed in this specification is described below. The invention disclosed in this specification is a buffer material for glass sheets to be interposed between glass sheets, the buffer material comprising cubic particles having a coating layer. An example embodiment is in which the coating layer comprises water-soluble cellulose, and the particles are sodium chloride particles. The invention disclosed in this specification is a buffer material for glass sheets to be interposed between glass sheets, the buffer material being a powder containing 50% by weight or more of a cubic crystal structure component. An example embodiment is in which the particles constituting the powder have a sodium chloride-type crystal structure. An example embodiment is in which the particles constituting the powder have a cubic shape. An example embodiment is in which the particles constituting the powder have two parallel planes. An example embodiment is in which the particles constituting the powder have flat surfaces. An example embodiment is in which the particles constituting the powder are at least one of sodium chloride particles, magnesium oxide particles, and alum particles. In one embodiment, the particles constituting the powder have an equivalent circle diameter of 10 μm to 250 μm. In another embodiment, the surfaces of the particles constituting the powder are covered with a biodegradable coating layer. In another embodiment, the coating layer contains a water-soluble inorganic salt and / or an organic acid. In another embodiment, the particles constituting the powder are sodium chloride particles, the surfaces of which are covered with a water-soluble cellulose coating layer. In another embodiment, the dispersion rate of the powder, when dispersed on a glass plate, is defined as (number of dispersed particles / total number of particles) with isolated particles being considered as dispersed particles, and the dispersion rate of the powder is 80% or more. The invention disclosed herein is a buffer material for glass plates to be interposed between glass plates, the buffer material being a powder containing 50% by weight or more of cubic-shaped particles. The invention disclosed in this specification is a buffer material for glass plates to be interposed between glass plates, the buffer material being a powder containing 50% by weight or more of particles having a cubic crystal structure and having a cubic shape formed by isotropic growth of the cubic crystal structure.The invention disclosed herein is a glass laminate comprising at least two glass plates laminated together via a buffer material for the glass plates, the buffer material being a powder containing 50% by weight or more of a component with a cubic crystal structure. The invention disclosed herein is a glass laminate comprising at least two glass plates laminated together via a buffer material for the glass plates, the buffer material being a powder containing particles having two parallel planes, one of the two parallel planes contacting one surface of the two glass plates and the other of the two parallel planes contacting the other surface of the two glass plates. In one embodiment, the particles constituting the powder are at least one of sodium chloride particles, magnesium oxide particles, and alum particles.

[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 to be placed between glass plates, the buffer material comprising cubic particles having a coating layer, the coating layer comprising water-soluble cellulose, the particles being sodium chloride particles, and the sodium chloride particle component comprising 50% by weight or more.

2. A buffer material for glass plates, which is a powder containing 50% or more by weight of components with a cubic crystal structure, and the particles that make up the powder are sodium chloride particles with a cubic shape.

3. The buffer material for glass plates according to claim 1 or 2, wherein the particles have an equivalent circle diameter of 10 μm to 250 μm.

4. The buffer material for glass plates according to claim 2, wherein the particles have a cellulose coating layer.

5. A glass laminate in which at least two glass sheets are laminated together with a buffer material for the glass sheets, wherein the buffer material for the glass sheets is a powder containing 50% by weight or more of sodium chloride particles having a cubic crystal structure.

6. A glass laminate in which at least two glass plates are laminated via a buffer material for glass plates, wherein the buffer material for glass plates is a powder containing 50% by weight or more of sodium chloride particles having two parallel planes, one of the two parallel planes being in contact with the surface of one of the two glass plates, and the other of the two parallel planes being in contact with the surface of the other of the two glass plates.

Images