Thermoplastic reflective glue, scintillating ceramic surface array and preparation method, CT detector

Abstract

This invention belongs to the field of radiation detection and medical device technology, specifically relating to a thermoplastic reflective adhesive, a scintillation ceramic array and its preparation method, and a CT detector. The thermoplastic reflective adhesive of this invention uses a specific thermoplastic resin as the main adhesive layer material, compounded with titanium dioxide-based reflective fillers and alumina, silica, and other absorbing fillers, and can be used to prepare scintillation ceramic arrays. The solution of this invention avoids the problems of long curing time and uneven shrinkage of the adhesive layer caused by high-temperature curing of thermosetting adhesives, significantly improving preparation efficiency. The prepared scintillation ceramic array exhibits excellent flatness and good batch consistency. After high and low temperature cycling tests, the flatness stability is excellent, and the product reliability is significantly improved. Assembling this scintillation ceramic array with a photoelectric converter to form a CT detector can effectively isolate optical crosstalk between pixels, ensure imaging signal fidelity, and meet the high-performance requirements of high-end medical imaging equipment.

Description

Technical Field

[0001] This invention belongs to the field of radiation detection and medical device technology, specifically relating to a thermoplastic reflective adhesive, a scintillation ceramic array and its preparation method, and a CT detector. Background Technology

[0002] Scintillators, as functional materials that can convert high-energy rays or particles into visible light, are core components for radiation detection and are widely used in fields such as medical imaging, high-energy physics, and nuclear safety. In X-ray computed tomography (X-CT) equipment, the scintillator array, as a key component of the detector, directly determines the core indicators such as image resolution and clarity, thus affecting the accuracy of disease diagnosis.

[0003] With the development of medical imaging technology, the market demand for X-CT image quality continues to increase. To obtain higher image resolution, scintillators need to be fabricated into array structures with smaller pixel sizes. A key step in the fabrication of such scintillator arrays is to use a reflective layer to bond and fix the cut scintillator pixels together to form an integrated array. This reflective layer must possess two core functions: first, to isolate optical crosstalk between pixels through efficient reflectivity, ensuring signal fidelity; second, to ensure the array as a whole has excellent planarity to avoid poor coupling with subsequent photodetectors, thereby guaranteeing the final performance of the imaging system.

[0004] The reflective adhesive used to form the reflective layer and its curing process are core factors determining the quality and efficiency of scintillator array fabrication. However, current technologies for preparing reflective layers for CT scintillator ceramic arrays still have significant shortcomings. Existing technologies mostly use thermosetting reflective adhesives, whose curing processes are time-consuming, severely limiting production efficiency and making it difficult to meet the needs of large-scale production. If high-temperature accelerated curing is used to shorten the time, the intense exothermic reaction can easily lead to uneven shrinkage of the adhesive layer, causing deterioration of the flatness of the scintillator ceramic array and compromising the structural stability of the product.

[0005] Furthermore, the planarity deviation control capability of scintillation ceramic arrays produced by existing processes is poor, with not only large overall deviation values ​​but also poor batch-to-batch consistency. In the actual operating conditions of CT equipment, scintillation arrays need to withstand high and low temperature cycling tests, and the planarity deviation of existing products fluctuates significantly under such environments, making it difficult to meet the long-term stable operation requirements of high-end equipment in terms of reliability and service life. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a thermoplastic reflective adhesive, a scintillation ceramic array and its preparation method, and a CT detector. The purpose of this invention is to overcome the deficiencies of existing technologies, such as low preparation efficiency of scintillation ceramic arrays, poor product flatness and batch consistency, and insufficient reliability under temperature-changing environments. It aims to provide a technical solution that significantly improves preparation efficiency while comprehensively optimizing product flatness, batch consistency, and environmental adaptability.

[0007] The first aspect of this invention provides a thermoplastic reflective adhesive, comprising, by weight percentage: Adhesive layer main material: 30%~45%; Reflective filler: 45%~60%; Absorbent filler: 5%~15%.

[0008] The adhesive layer material is selected from at least one of polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, and polystyrene; the reflective filler is titanium dioxide; and the absorbent filler is selected from at least one of alumina and silica.

[0009] As a further optimization of the above-mentioned thermoplastic reflective adhesive, the reflective filler is selected from at least one of R-103, R-104, R-960, and R-902+.

[0010] As a further optimization of the aforementioned thermoplastic reflective adhesive, it comprises the following components by weight percentage: Adhesive layer main material: polymethyl methacrylate, 35±2%; Reflective fillers: Titanium dioxide R-104, 30±2%; Titanium dioxide R-960, 25±2%; Absorbent filler: alumina, 10±2%.

[0011] As a further optimization of the aforementioned thermoplastic reflective adhesive, by weight percentage, it includes: Adhesive layer main material: polymethyl methacrylate, 40±2%; Reflective fillers: Titanium dioxide R-104, 35±2%; Titanium dioxide R-960, 20±2%; Absorbent filler: silica, 5±2%.

[0012] A second aspect of this invention provides a method for preparing a scintillation ceramic array, comprising the following steps: S1: Provide a scintillator ceramic substrate, fix it on the substrate, form crisscrossing grooves on the surface of the scintillator ceramic substrate by cutting, and clean and dry the scintillator ceramic substrate after grooving. S2: Heat and melt any of the above thermoplastic reflective adhesives, fill them into the grooves under vacuum conditions, and form a reflective layer on the surface of the ceramic substrate that extends beyond its surface. After filling, perform vacuum degassing treatment. S3: Place the filled ceramic substrate in a clean environment to cool and solidify naturally; S4: Remove the substrate used for fixing, and polish the ceramic substrate with the reflective layer after curing: polish the surface reflective layer to the predetermined thickness, polish the back of the surface reflective layer to remove the unfilled scintillation ceramic part, until the reflective layer material in the groove is exposed, forming a flat light-emitting surface. S5: By cutting away the excess parts around the perimeter, a scintillation ceramic array with a pixel array structure is obtained.

[0013] As a further optimization of the above-mentioned method for preparing scintillating ceramic arrays, in step S1, the scintillator ceramic substrate is a GAGG ceramic sheet.

[0014] As a further optimization of the above-mentioned method for preparing scintillation ceramic arrays, in step S1, the groove depth is 1.8-3.5 mm, the groove width is 0.07-0.15 mm, and the groove spacing is 0.2-0.4 mm.

[0015] As a further optimization of the above-mentioned method for preparing scintillation ceramic arrays, in step S3, the natural cooling and curing time is 1~4h, preferably 2±0.5h.

[0016] A third aspect of the present invention provides a scintillation ceramic array, which is prepared by any of the above-described preparation methods.

[0017] A fourth aspect of this invention provides a CT detector comprising the aforementioned scintillation ceramic array and a photoelectric converter. Under X-ray irradiation, visible light emitted from the scintillation ceramic array acts on the photoelectric converter via its emitting surface, and the photoelectric converter generates an electrical signal under the influence of the visible light. Specifically, under X-ray irradiation, incident X-rays act on the pixelated scintillator substrate of the scintillation ceramic array, and the substrate generates visible light through stimulated emission. The reflective layer within the trenches efficiently reflects and confines the visible light, effectively blocking optical crosstalk between adjacent pixels and ensuring the purity and transmission fidelity of the light signal from a single pixel. For each pixel, the visible light generated by excitation is blocked by the reflective layer and exits from the emitting surface of the pixel, illuminating the photosensitive area of ​​the photoelectric converter corresponding to that pixel. After receiving the visible light signal, the photoelectric converter performs photoelectric conversion, generating an electrical signal with a defined mapping relationship to the light intensity and outputting it outward, providing a high-quality raw signal for image reconstruction in the CT imaging system. This CT detector, relying on the excellent flatness and adaptability to high and low temperature environments of the scintillation ceramic array, can maintain stable signal output under complex operating conditions, which helps to improve imaging clarity and service life, and better meet the requirements of high-end medical imaging equipment for long-term reliable operation of the detector.

[0018] Beneficial effects This invention formulates a novel reflective adhesive and explores a new method for preparing scintillation ceramic arrays, significantly improving preparation efficiency, avoiding process defects in the curing process of existing reflective adhesives, and resulting in products with excellent flatness control, smaller deviations, and higher batch-to-batch concentration. The stability and consistency of the production process are significantly improved. After high and low temperature cycling reliability testing, the scintillation ceramic arrays prepared by this invention exhibit small fluctuations in flatness deviation and no obvious extreme anomalies, demonstrating superior stability and reliability under temperature-changing environments. Examples 5 and 7, as the optimal solutions of this invention, demonstrate more significant advantages in all aspects of performance, achieving comprehensive optimization of preparation efficiency, product flatness, batch consistency, and environmental reliability, better meeting the high-performance application requirements of CT scintillation ceramic arrays. Attached Figure Description

[0019] Figure 1 Box plots showing the overall flatness deviation of the scintillation ceramic arrays in Examples 1-7 and Comparative Example 1.

[0020] Figure 2 The diagram shows the flatness deviation field distribution of the scintillation ceramic array in Example 7.

[0021] Figure 3 The flatness deviation field distribution diagram is shown for the scintillation ceramic array of Comparative Example 1. Detailed Implementation

[0022] The present invention is further illustrated below with specific embodiments. These embodiments are exemplary and intended to illustrate the problem and explain the present invention, and are not intended to be limiting.

[0023] Examples 1-7 The scintillator ceramic array is fabricated using the following process.

[0024] Step S1: The scintillator ceramic substrate is bonded to the fixed glass substrate using rosin heating. The scintillator substrate used is a GAGG ceramic sheet, 15mm in length, 8mm in width, and 3mm in thickness.

[0025] Step S2: Use a multi-wire cutting machine to cut grooves on the surface of the ceramic sheet, with a groove depth of 2.6mm. Cut 15 grooves parallel to the long side, 13.5mm inwards from the edge of the ceramic substrate. The groove width is 0.1mm, and the spacing is 0.3mm.

[0026] Step S3: Rotate the ceramic substrate and the glass substrate as a whole by 90° and cut 31 grooves along the direction parallel to the short side by 7mm. The groove width is 0.1mm and the spacing is 0.3mm.

[0027] Step S4: After grooving, the ceramic substrate is ultrasonically cleaned with anhydrous ethanol for 3 minutes, then vacuum dried at 60℃, and plasma cleaned for 5 minutes before use. Step S5: Prepare reflective adhesive. Add thermoplastic material and filler to the reflective adhesive in a vacuum mixer according to the reflective adhesive ratio provided in Table 1, and vacuum mix at 150°C for 25 minutes. Then extrude and granulate the mixture. The granulation particle size is 3~5μm. Then cool and dry at room temperature to obtain thermoplastic reflective adhesive.

[0028] Step S6: Apply high-temperature tape around the ceramic substrate and the glass substrate. Melt the thermoplastic reflective adhesive obtained in step S5 at 160°C and extrude it into the surface of the ceramic substrate. After the thermoplastic reflective adhesive has fully filled the grooves on the surface of the ceramic substrate and continues to fill to a thickness of 1 mm, vacuum degas for 10 minutes.

[0029] Step S7: Place the filled and glued ceramic substrate in a clean box and let it cool naturally before removing it.

[0030] Step S8: Remove the high-temperature tape around the edges, fix the glass substrate onto the grinding machine, and grind the surface adhesive layer to a thickness of 0.2mm; heat and melt the rosin, remove the ceramic substrate with the reflective layer, flip it over, and grind it on the grinding machine to remove approximately 0.3mm of excess un-coated scintillation ceramic portion, exposing the reflective layer surface with checkerboard grooves, making the overall thickness 2.7mm. Then use a precision dicing machine to remove the excess crystal around the edges, thus obtaining the CT scintillation ceramic array with a pixel specification of 32×16.

[0031] The operation steps of Examples 1 to 7 are basically the same, the only difference is the raw materials and proportions used to prepare the thermoplastic reflective adhesive. For specific formulas, please refer to Table 1.

[0032] Table 1 Reflective Adhesive Ingredient List Comparative Example 1 Comparative Example 1 uses a thermosetting reflective adhesive. The initial steps of its operation are exactly the same as steps S1-S4 in the example, and the subsequent steps are exactly the same as step S8 in the example. Only steps S5-S7 are different, and they are named steps S5b-S7b. The reflective adhesive formulation is implemented according to Table 1. The specific steps are as follows: Step S5b: Prepare reflective adhesive. Add EP and filler according to the ratio in the vacuum planetary mixer tank, and vacuum mix for 3 minutes to obtain reflective adhesive.

[0033] Step S6b: Apply high-temperature adhesive tape around the ceramic substrate and the glass substrate. Slowly drip the reflective adhesive obtained in step 5b into the grooves on the surface of the ceramic substrate to fill the grooves completely. Then fill the grooves with an additional 1mm thickness and vacuum degas for 10 minutes.

[0034] Step S7b: Place the ceramic substrate filled with reflective adhesive into an oven and heat at 80°C for 20 hours, then raise the temperature to 100°C and heat for another 20 hours. After stopping the heating and allowing it to cool naturally, remove it from the oven.

[0035] Results and Analysis Based on the above preparation process, it can be seen that the curing of thermoplastic reflective adhesives only requires natural cooling, with a curing time of approximately 2 hours; while thermosetting reflective adhesives typically use epoxy resins, requiring a much longer curing time, usually around 40 hours. If a high-temperature curing method is used to shorten the curing time, significant exothermic phenomena will occur, thus affecting the flatness of the adhesive layer. Therefore, the solution of this invention has a significant efficiency advantage over commonly used thermosetting reflective adhesive solutions in the preparation of scintillating ceramic arrays.

[0036] To verify product reliability, high and low temperature cycling reliability tests were conducted on the scintillation ceramic arrays (20 pieces per group) prepared in each embodiment and comparative example. The specific test procedure is as follows: First, the test chamber was adjusted to 25°C and 50% relative humidity, and the samples were placed in and pretreated for 2 hours. Then, the temperature was lowered to -20°C at a rate of 3°C / min (humidity uncontrolled) and held for 3 hours. Next, the temperature was increased to 60°C at a rate of 3°C / min (humidity uncontrolled) and held for 3 hours. Then, the temperature was lowered to 25°C at a rate of 3°C / min, which served as the starting point for the temperature cycle. The above steps of increasing the temperature to 60°C at 3°C / min and decreasing it to 25°C at 3°C / min were repeated for a total of 5 cycles. Finally, the samples were treated at 25°C and 50% relative humidity for 2 hours. After the treatment, the flatness deviation of each scintillation ceramic array sample in each embodiment and comparative example was detected, and a flatness deviation field distribution map of a single sample and a box plot of the overall flatness deviation were plotted.

[0037] Box plots of the overall flatness deviation of the scintillation ceramic arrays in each embodiment and comparative example are shown below. Figure 1 As shown, the flatness deviation field distribution diagrams of Example 7 and Comparative Example 1 are respectively as follows: Figure 2 and Figure 3 As shown. Figure 1In the diagram, the colored box represents the interquartile range, from the lower quartile (25th percentile) to the upper quartile (75th percentile), covering the middle 50% of the sample data within the group. A narrower box indicates a more concentrated flatness deviation in the middle 50% of samples; a wider box indicates a more dispersed middle data. The horizontal line within the box represents the median (50th percentile), representing the median value within the group. A lower median indicates a smaller overall flatness deviation; a higher median indicates a larger overall deviation. The vertical lines extending from the upper and lower edges of the box are the upper and lower whiskers, representing the overall distribution range of the data within the group (from minimum to maximum). Longer whiskers indicate greater fluctuations in the flatness deviation of the entire group of samples; shorter whiskers indicate smaller fluctuations. Scattered points outside the whiskers (such as the two points in Example 6) are outliers, i.e., extreme data that significantly deviate from the population distribution, indicating that the flatness deviation of individual samples deviates abnormally from other samples within the group. Figure 2 and Figure 3 The distribution of flatness deviation on the surface of the scintillation ceramic array is shown in the form of a color pseudo-color map. The color scale on the right is a quantitative scale for flatness deviation, ranging from -0.02mm to 0.02mm: the red area represents positive deviation (protrusion), the blue area represents negative deviation (depression), and the green area represents deviation close to 0mm (the area with the best flatness).

[0038] according to Figure 1 It can be seen that, compared with Comparative Example 1, the scintillation ceramic arrays prepared in most examples show significant advantages in flatness control and reliability. The median flatness deviation of Comparative Example 1 is higher than that of most examples, indicating that the overall flatness deviation of the samples prepared in these examples is smaller. The wider chamber width of Comparative Example 1 indicates that the flatness deviation of the middle 50% of its samples is more dispersed, and the process stability is weaker; while the narrower chambers of most examples indicate that the deviation concentration of the middle batch of samples is higher, and the production process is more stable. The longer upper and lower whiskers of Comparative Example 1 are than those of most examples, indicating that the flatness deviation of the entire group of samples fluctuates more, and the reliability is insufficient after high and low temperature cycling; indicating that the flatness stability of the present invention is better under temperature change environment.

[0039] In all embodiments, Embodiments 5 and 7 exhibited significantly better flatness control than the other embodiments. Regarding overall deviation, the median flatness deviation of Embodiments 5 and 7 was the lowest among all groups, indicating that their overall flatness deviation level was within the optimal range, and their surface flatness was the best. In terms of batch consistency, the box width of Embodiments 5 and 7 was the narrowest among all embodiments, indicating that the flatness deviation was most concentrated in the middle 50% of the samples, demonstrating optimal consistency and controllability of the production process. Regarding reliability and stability, Embodiments 5 and 7 had the shortest upper and lower whisker lines and no obvious outliers, indicating that the flatness deviation fluctuation of the entire sample group was minimal, with almost no extreme deviation samples after high and low temperature cycling. Their reliability and batch stability were far superior to other embodiments, further verifying the significant technical superiority of the solutions in Embodiments 5 and 7.

[0040] Material Name Lookup Table PVC: Polyvinyl chloride; PMMA: Polymethyl methacrylate; PET: Polyethylene terephthalate; PS: Polystyrene; EP: Epoxy resin, the type used in Comparative Example 1 is HH703; GAGG: Gadolinium aluminum gallium garnet (chemical formula Gd3Al2Ga3O) 12 ); R-103, R-104, R-960, and R-902+ are all titanium dioxide grades.

[0041] The above embodiments are exemplary and are intended to illustrate the technical concept and features of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A thermoplastic reflective adhesive, characterized in that, By weight percentage, including: Adhesive layer main material: 30%~45%; Reflective filler: 45%~60%; Absorbent filler: 5%~15%; The adhesive layer material is selected from at least one of polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, and polystyrene; the reflective filler is titanium dioxide; and the absorbent filler is selected from at least one of alumina and silicon dioxide.

2. The thermoplastic reflective adhesive according to claim 1, characterized in that, The reflective filler is selected from at least one of R-103, R-104, R-960, and R-902+.

3. The thermoplastic reflective adhesive according to claim 1, characterized in that, It consists of the following components by weight percentage: Adhesive layer main material: polymethyl methacrylate, 35±2%; Reflective fillers: Titanium dioxide R-104, 30±2%; Titanium dioxide R-960, 25±2%; Absorbent filler: alumina, 10±2%.

4. The thermoplastic reflective adhesive according to claim 1, characterized in that, By weight percentage, including: Adhesive layer main material: polymethyl methacrylate, 40±2%; Reflective fillers: Titanium dioxide R-104, 35±2%; Titanium dioxide R-960, 20±2%; Absorbent filler: silica, 5±2%.

5. A method for preparing a scintillation ceramic array, characterized in that, Includes the following steps: S1: Provide a scintillator ceramic substrate, fix it on a substrate, form crisscrossing grooves on the surface of the scintillator ceramic substrate by cutting, and clean and dry the scintillator ceramic substrate after grooving. S2: The thermoplastic reflective adhesive according to any one of claims 1-4 is heated and melted, and filled into the groove under vacuum conditions, and a reflective layer extending beyond the surface of the ceramic substrate is formed. After filling, vacuum degassing treatment is performed. S3: Place the filled ceramic substrate in a clean environment to cool and solidify naturally; S4: Remove the substrate used for fixing, and polish the ceramic substrate with the reflective layer after curing: polish the surface reflective layer to the predetermined thickness, polish the back of the surface reflective layer to remove the unfilled scintillation ceramic part, until the reflective layer material in the groove is exposed, forming a flat light-emitting surface. S5: By cutting away the excess parts around the perimeter, a scintillation ceramic array with a pixel array structure is obtained.

6. The method for preparing a scintillation ceramic array according to claim 5, characterized in that, In step S1, the scintillator ceramic substrate is a GAGG ceramic sheet.

7. The method for preparing a scintillation ceramic array according to claim 5, characterized in that, In step S1, the groove depth is 1.8-3.5mm, the groove width is 0.07-0.15mm, and the groove spacing is 0.2-0.4mm.

8. The method for preparing a scintillation ceramic array according to claim 5, characterized in that, In step S3, the natural cooling and curing time is 1~4 hours.

9. A scintillation ceramic array, characterized in that, It is prepared by the preparation method according to any one of claims 5-8.

10. A CT detector, characterized in that, The device includes the scintillation ceramic array and photoelectric converter as described in claim 9. Under X-ray irradiation, visible light emitted by the scintillation ceramic array acts on the photoelectric converter through the light-emitting surface, and the photoelectric converter generates an electrical signal under the action of visible light.

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