JP2005308975A - Display substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display substrate with which the breakage due to the deformation of a display panel hardly occurs. <P>SOLUTION: The display substrate has the nature that the stress at the time of a face push under the following conditions attains <110 MPa. The conditions are a sample size: 40 mm square, a supporting method of a sample: supported only at each peripheral edge 5 mm, a face push method: the central part of the sample is pressed 0.5 mm perpendicularly to the same surface, and a stress measurement area: the central part of the sample. As a result, the occurrence of the breakage is substantially prevented even if deformation is generated in the sample by exertion of the stress to the display panel. Also, the thickness reduction of the substrate is made possible while the strength of the substrate is maintained and therefore the weight reduction and thickness reduction of the display panel can be achieved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display substrate used for a liquid crystal display panel, an EL display panel and the like.

  A display module using a liquid crystal display panel, an EL display panel or the like is characterized by being thin and lightweight. Taking advantage of this feature, these display modules are widely used as display units of mobile terminal devices such as mobile phones and digital cameras.

A glass plate having a thickness of about 0.7 to 1.1 mm is generally used for the substrate constituting the display panel, but a glass plate for further thinning has also been proposed (Patent Document 1). In some cases, plastic plates are also used.
JP 2002-308643 A

  Meanwhile, some portable terminal devices such as mobile phones and PDAs have a folding structure. In a device having such a structure, the display is protected because it is folded when not in use. However, some displays used for digital cameras and the like are always exposed regardless of whether they are used or not. In these devices, external stress may be directly applied. In addition, mobile terminals are often stored in clothes and the like, and bending stress may be applied to the device for a long time when sitting. Therefore, in this type of equipment, there is a concern that the glass substrate is damaged due to the deformation of the display panel. In the case of a plastic substrate, plastic deformation may occur due to the application of stress, which may cause display defects.

  An object of the present invention is to provide a display substrate that is not easily damaged by deformation of the display panel.

  In order to produce a display panel that is not easily damaged, it is important that the display substrate has high mechanical strength. As a method for evaluating the mechanical strength, a method is generally used in which a sample is deformed until the sample is broken and a stress that leads to the fracture is measured, such as a three-point bending test or a four-point bending test. However, according to the knowledge of the present inventors, for example, in the case of a liquid crystal display module, the deformation (deflection) of the mounted panel is limited to a certain amount or less due to the presence of a light guide plate or the like on the back of the panel. In this evaluation method, it became clear that appropriate evaluation was not possible. And, as a result of earnestly devised, when a certain amount of deformation has occurred, the magnitude of the stress generated in the substrate is used as a parameter of mechanical strength, and the substrate is designed so that the value is a specific value or less. The inventors have found that the object can be achieved and have proposed the present invention.

  That is, the display substrate of the present invention is characterized in that the stress when the surface pressing is performed under the following conditions is less than 110 MPa.

Sample size: 40 mm square Sample support method: Supported by each peripheral edge 5 mm only Surface pressing method: Sample center portion pressed 0.5 mm Stress measurement site: Sample center portion The display substrate of the present invention has a substrate thickness of 0 It is desirable that the thickness is less than 5 mm and / or the Young's modulus is 70 GPa or less.

  The display substrate of the present invention is used for a substrate of a display panel incorporated in a display module, and the display module has a display panel and components provided on the back side thereof, It is preferable that the display panel has a structure in which deformation of the display panel is restricted by the constituent members, that is, a structure in which the display panel does not deform more than a certain amount.

  The display substrate of the present invention is preferably a liquid crystal display panel substrate.

  The display substrate of the present invention is preferably a display panel substrate having a panel size of 20 inches or less.

  If the substrate of the present invention is used, even if stress is applied to the display panel to cause deformation, the substrate can be hardly damaged. Further, since the thickness of the substrate can be reduced while maintaining the strength of the substrate, it is possible to reduce the weight of the display panel and reduce the thickness.

  Since the back of the liquid crystal display panel is equipped with a diffuser plate, light guide plate, etc. that diffuses light from the backlight, the panel (substrate) contacts these components when the panel (substrate) is deformed to some extent, and the deformation of the substrate is restricted. Is done. Therefore, when considering the mechanical strength of the substrate incorporated in the display module, the magnitude of the stress generated when the amount of deformation of the substrate is constant is important, and it is important to evaluate this.

  From such a viewpoint, the display substrate of the present invention specifies the present invention by using, as a parameter, a stress value generated when the substrate changes by a certain amount. The method for measuring the stress will be described in detail below.

  First, a 40 mm square sample for evaluation is prepared. If the substrate itself is larger than the size, it may be evaluated after cutting into a 40 mm square. When the substrate itself has already been processed to a size smaller than the above size, for example, it may be cut into a 40 mm square from the original plate before processing and used for this evaluation. In any case, it is necessary to avoid changing the thickness and surface state of the substrate itself.

  Next, the sample for evaluation is supported in a state where the central portion is deformable. That is, the sample is supported only by the peripheral edge (each side is 5 mm wide), and the sample central portion (30 mm square) is in a deformable state.

  Thereafter, the central portion of the sample for evaluation is pressed to deflect the central portion of the sample by 0.5 mm, and the stress generated at the central portion of the sample at this time is measured.

  The substrate of the present invention desirably has a stress measured by the above method of less than 110 MPa, preferably less than 100 MPa, more preferably less than 80 MPa, and most preferably less than 50 MPa. If this value decreases, it can be said that the stress generated in the substrate when it is deformed by a certain amount is reduced, and the substrate is less likely to be damaged (brittle material such as glass) or plastically deformed (plastic material).

  In the present invention, in order to reduce the stress value caused by the deformation of the substrate, the substrate thickness may be reduced or the substrate may be made of a material having a low Young's modulus.

  The thinner the substrate thickness, the smaller the stress generated on the substrate when it is deformed by a certain amount. Specifically, it is desirable to be less than 0.5 mm, less than 0.45 mm, less than 0.4 mm, less than 0.35 mm, less than 0.3 mm, less than 0.25 mm, and optimally less than 0.2 mm.

The Young's modulus of the substrate is desirably 70 GPa or less, particularly 68 GPa or less, more preferably 66 GPa or less, and most preferably 63 GPa or less. The Young's modulus is determined by the material of the substrate. The substrate is made of glass, in its composition by _{mass%, SiO 2 50~75%, Al} 2 O 3 0~20%, B 2 O 3 3~20%, alkali metal oxides 0-20%, alkaline earth When it has a composition of 0 to 20% of metal oxide and 0 to 10% of ZnO, it is possible to effectively lower the Young's modulus especially by reducing the amount of B ₂ O _{3 and} the content of MgO and ZnO. . Specifically, when it is desired to obtain a Young's modulus of 70 GPa or less, by mass%, SiO ₂ 50 to 68%, Al ₂ O ₃ 13 to 19%, B ₂ O _{3 3 to} 15%, MgO 0 to 15, It is preferable to use a glass having a composition of CaO 0-15, SrO 0-15, ZnO 0-10%. Further, when it is desired to obtain a Young's modulus of 68 Gpa or less, it is in mass%, SiO ₂ 53-70%, Al ₂ O ₃ 12-18%, B ₂ O ₃ 5-18%, MgO 0-12, CaO 0-12. It is preferable to use glass having a composition of SrO 0-12, ZnO 0-7%. Furthermore, when it is desired to obtain a Young's modulus of 66 Gpa or less, SiO ₂ 55 to 70%, Al ₂ O ₃ 10 to 17%, B ₂ O ₃ 7 to 20%, MgO 0 to 10, CaO 0 to 10, SrO 0 It is preferable to use a glass having a composition of -10 to ZnO 0 to 5%. When the substrate is used for a device such as an active matrix driving TFTLCD or an organic EL, it is desirable that the substrate does not substantially contain an alkali metal oxide, but in the case of other devices, the substrate contains an alkali metal oxide. Can do. The substrate material is not limited to glass, and may be plastic.

Considering that the substrate of the present invention is used for a terminal such as a mobile phone, the density of the substrate is preferably less than 2.5 g / cm ³ . More preferably less than 2.45 g / cm ^3, more preferably less than 2.40 g / cm ^3, and most preferably less than 2.35 g / cm ^3.

  In addition, since the substrate of the present invention is used for display applications, the transmittance of the substrate is 88% or more, particularly 89% or more, more preferably 90% or more, optimally at wavelengths of 400 nm, 500 nm, 600 nm and 700 nm. It is desirable that it is 91% or more. Furthermore, since there is a possibility of causing a minute dimensional change when exposed to a high temperature during the manufacturing process of TFT-LCD, the glass transition temperature which is an index of heat resistance is 200 ° C. or higher, preferably 250 ° C. or higher. The temperature is preferably 300 ° C. or higher, and most preferably 400 ° C. or higher.

  The display substrate of the present invention is a small substrate, specifically 20 inches or less, particularly 10 inches or less (PDA use, mobile phone use, digital camera use, etc.), and further 5 inches or less (mobile phone use, digital camera use). And so on), a remarkable effect can be obtained. That is, when a certain amount of deformation occurs, the smaller the substrate size, the larger the ratio of the amount of deflection with respect to the substrate size.

  Table 1 shows examples (sample Nos. 1 to 12) and conventional examples (sample No. 13) of the present invention.

  Each glass sample in the table was prepared as follows. First, a batch prepared by mixing the raw materials in a predetermined ratio was put in a platinum crucible, melted at 1650 ° C. for 24 hours, and then poured onto a carbon plate and formed into a plate shape. The glass immediately after molding was placed in an annealer maintained at 750 ° C. and allowed to cool to room temperature.

  The sheet glass after being allowed to cool was annealed according to the following schedule (FIG. 1).

(1) Temperature rise from room temperature to 762 ° C at a rate of 5 ° C / min (2) Hold at 762 ° C for 30 minutes (3) Temperature drop to 582 ° C at a rate of 3 ° C / min (4) 10 ° C / min to room temperature Temperature drop at speed A sample for evaluation was prepared using the plate-like glass thus prepared, and the density, glass transition temperature, transmittance, Young's modulus, and stress during surface pressing were measured.

  The density was measured by the well-known Archimedes method.

  The glass transition temperature was measured based on the method of ASTM C336-71.

  A transmittance of 40 mm × 40 mm × 0.3 mm was prepared, and the transmittance of each wavelength was measured using UV-3100PC (manufactured by Shimadzu Corporation) under the condition of slit width: 2.0 nm.

  The Young's modulus was measured by a resonance method by preparing a sample of 20 mm × 40 mm × 2 mm.

  The stress at the time of surface pressing was evaluated as follows.

  First, a sample for evaluation was cut out to a size of 40 mm × 40 mm from the plate glass, processed to a predetermined plate thickness, and mirror-polished to prepare Sample 1 for evaluation. In addition, a stainless steel jig 4 having an opening of 30 mm × 30 mm in the sample mounting portion was prepared.

Next, after the sample surface was washed with ethanol, 1 drop of instant adhesive (CN (general purpose) manufactured by Tokyo Sokki Kenkyujo) was dropped on strain gauge (BFLA-5-3 Tokyo Sokki Kenkyujo) 2. The sample 1 was pressed against the center of the sample 2 for 2 minutes for adhesion. The pressing was performed on a polyethylene sheet. At that time, attention was paid so that the side direction of the strain gauge 2 and the side of the sample 1 were parallel. (See Figure 2)
After attaching the strain gauge 2 and leaving it to stand at room temperature in the atmosphere for 30 minutes or more, the cord 3 of the strain gauge 2 is connected to the data logger (TDS-601 Tokyo Sokki Kenkyujo) through the opening of the jig 4. . Subsequently, the sample 1 was placed on the jig 4 so that the adhesion surface of the strain gauge 2 was on the lower side. At this time, the sample 1 was placed so that the four sides of the opening of the jig 4 and the four sides of the sample 1 were parallel to each other, and the periphery of the sample 1 was supported on the upper surface of the jig 4 with a width of 5 mm. The skewness at this point was set to zero.

  Subsequently, the micrometer 5 was installed so that the tip (spherical shape of R = 3.6 mm) was at the center of the sample 1, and was brought close to the tip of the micrometer 5 in contact with the sample 1, and the scale at that time was read. . Further, the scale of the micrometer 5 was advanced by 0.5 mm from the read value. That is, Sample 1 was bent by 0.5 mm.

  The strain of the sample 1 deflected by 0.5 mm in this way was measured with the strain gauge 2, and the stress was calculated by applying the Young's modulus to this value.

  The Young's modulus in the table was measured by a resonance method by preparing a sample of 20 mm × 40 mm × 2 mm. The density was measured by the well-known Archimedes method.

  As can be seen from the table, no. As for the samples 1-12, the stress at the time of surface pressing is as small as less than 110 MPa. On the other hand, No. In the 13 samples, the stress at the time of surface pressing was 161 MPa.

  Next, No. having the same composition. 1 (Example) and No. 1 For 13 (conventional example), the probability of destruction was determined by the following method.

  First, sample no. 1, no. For No. 13, a biaxial bending test (ring-on-ring test) was performed under the following conditions.

Equipment used: Autograph made by Shimadzu Supporting circle diameter: 2.5cm
Load circle diameter: 1.25cm
Load speed: 1 mm / min The fracture stress is calculated based on the obtained fracture load, the logarithm of the fracture stress [MPa] on the horizontal axis, and the fracture probability determined by the average rank method on the vertical axis is F [%]. (Ln (1 / (1-F)) was plotted, and Weibull plots of Sample No. 1 and No. 13 were created, respectively, and the surface pressing of Sample No. 1 and No. 13 obtained in Example 1 was performed. Was substituted into the approximate curve of each Weibull plot to determine the probability of failure.

As a result, no. No. 1 failure probability (6 × 10 ⁻³ %) It is 1/5 or less of that of 13 (33 × 10 ⁻³ %), and it can be understood that the probability of destruction is extremely small.

  The present invention can be used not only as a substrate of a liquid crystal display or an EL display but also as a cover glass of a solid-state imaging device.

It is explanatory drawing which shows the annealing schedule of the sheet glass for evaluation. It is explanatory drawing which shows the state which attached the strain gauge to the sample. It is explanatory drawing which shows the method of measuring the stress at the time of surface pressing.

Explanation of symbols

1 Sample 2 Strain gauge 3 Strain gauge cord 4 Jig 5 Micrometer

Claims (6)

A display substrate characterized by having a property that the stress when the surface is pressed under the following conditions is less than 110 MPa.
Sample size: 40 mm square Sample support method: Supported by each peripheral edge 5 mm only Surface pressing method: 0.5 mm perpendicular to the sample surface at the center of the sample Stress measurement site: Sample center   2. The display substrate according to claim 1, wherein the thickness of the substrate is less than 0.5 mm.   The display substrate according to claim 1, wherein the display substrate is made of a material having a Young's modulus of 70 GPa or less.   A display panel substrate incorporated in a display module, wherein the display module has a display panel and a constituent member provided on a back side of the display panel, and deformation of the display panel is regulated by the constituent member, 2. The display substrate according to claim 1, wherein the display substrate has a structure that does not deform more than a certain amount.   2. The display substrate according to claim 1, which is a substrate for a liquid crystal display panel.   2. The display substrate according to claim 1, wherein the display substrate is a display panel substrate having a panel size of 20 inches or less.